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Bad power?

Discuss miniature cannons built from things such as pill bottles and pen caps.
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Unread postAuthor: Spudinator » Tue Aug 14, 2007 1:17 am

Pnuemos are better for smaller heavier projectiles, the higher/longer pressure spike tends to accelerate them much better, Combustions are better for the lighter stuff...


And BP sucks btw, its weak compared to some of my recent testings lol, 'cough' steel BB through 4.5" of cedar/4500 fps 'cough' :P

But do try to keep solid propellants out of the discussions, the rules here are the same as they were at spudtech, so knock it off
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Unread postAuthor: frankrede » Tue Aug 14, 2007 2:49 am

Agreed.
My large combustions are great for launching light weight items far but when it comes my smaller combustions, Its hard to launch a bolt slug, then a again its a 3/4" wide bolt, but my pneumatic of equal size will put the bolt through sheetmetal.
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Unread postAuthor: f.c » Tue Aug 14, 2007 4:46 am

agreed. probably because combustion cannons reach a max pressure of about 80 psi when alot of people use there pneumatics at over 100 psi it makes a big difference.
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Unread postAuthor: Spudinator » Tue Aug 14, 2007 3:09 pm

Standard combustions peak at 40-45 PSI, they work so well for accelerating light projectiles because the gas temp is so high (hotter the gas is the lighter it becomes, which means it flows faster than standard-temp air).
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Unread postAuthor: spudd » Fri Aug 17, 2007 9:43 am

oh yeah! i never thought about that!
why do a cannon that runs on expensive gas when you can run it on air.
thanks guys
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Unread postAuthor: jimmy101 » Fri Aug 17, 2007 7:40 pm

Spudinator wrote:Standard combustions peak at 40-45 PSI, they work so well for accelerating light projectiles because the gas temp is so high (hotter the gas is the lighter it becomes, which means it flows faster than standard-temp air).

Spudinator, that is the second time you've posted that. It is wrong. Heating a gas in a closed chamber does not make it lighter. Mass is conserved.

Pop Quiz:
Which weighs more, a pound of air at 72F, or a pound of air at 4000F?

Heating a gas will make it flow faster, so you got that part right.

Heating a gas in an open or expandable container will cause it to expand which lowers its density, not its mass or weight
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Unread postAuthor: frankrede » Fri Aug 17, 2007 7:43 pm

jimmy101 wrote:
Spudinator wrote:Standard combustions peak at 40-45 PSI, they work so well for accelerating light projectiles because the gas temp is so high (hotter the gas is the lighter it becomes, which means it flows faster than standard-temp air).

Spudinator, that is the second time you've posted that. It is wrong. Heating a gas in a closed chamber does not make it lighter. Mass is conserved.

Pop Quiz:
Which weighs more, a pound of air at 72F, or a pound of air at 4000F?

Heating a gas will make it flow faster, so you got that part right.

Heating a gas in an open or expandable container will cause it to expand which lowers its density, not its mass or weight


Pop Quiz: They weigh the same.

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spudd wrote:oh yeah! i never thought about that!
why do a cannon that runs on expensive gas when you can run it on air.
thanks guys
Expensive gas? ya 3$ for 200+ shots is killing me. A compressor on the other hand uses electricity, shich costs money/
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Unread postAuthor: Spudinator » Fri Aug 24, 2007 11:01 pm

Meh, kinda what I meant really. Its been a bit since I played with spudguns, so I'm a little rusty in some areas, pardon me.
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